It has been the practice to prefabricate handrails for use on curved or spiral stairways out of laminated wood sections. These rail sections must then be assembled at the site to conform to a particular desired curvature or pitch in accordance with the requirements and specifications at the intended site. It has also been proposed to custom fabricate handrails at the site in order to more readily conform to the particular specifications and to avoid the time and expense of packaging and shipping a wide variety of curved rail sections needed to meet different specifications. Whether the handrail is prefabricated or custom fabricated at the site, a particular problem confronting the fabricator is in forming the necessary compound curvature or bend in the rail which will avoid twisting of the rail when it is bent to conform to the slope and curvature of the stairway. In other words, when the handrail is bent to follow or conform to a particular curvature along a spiral or curved stairway, the slope of the stairway will tend to introduce an unwanted twist into the rail section about its own axis. This is especially true of handrails formed out of elongated, laminated strips of wood which are adhered together into a desired profile and allowed to cure or set into a particular configuration which will follow the curvature of the staircase.
Representative of the approaches taken in the past are U.S. Letters Pat. No. 3,107,708 to R. H. Savage which employs a steel form having an L-shaped cross-section and which must be curved or otherwise shaped into the configuration of the particular curvature of member to be formed and which is employed in combination with C-shaped clamps disposed at right angles to one another. U.S. Letters Pat. No. 3,879,062 to J. B. Lappin, Jr. exemplifies a somewhat different method of forming curved laminated rails using what is described as helical work holders or supporting units which can be adjusted into different positions above a common shaft. Other patents of general interest in this field are U.S. Letters Pat. Nos. 2,902,948 to J. Morros; 4,602,766 to H. Naka et al; 3,733,055 to W. J. Hughes, Jr.; 3,922,453 to R. F. Seery; 4,132,391 to S. Takenaga; 4,646,490 to H. Naka et al; 3,835,904 to J. S. Sumner and 4,256,287 to R. A. Birmingham. Nevertheless, there is lacking any suggestion or disclosure of an on-site forming method which avoids the use of specially contoured forms but enables compound bending in place of laminated wood sections into the desired curvature and pitch while overcoming problems of undesirable twisting and distortion of the section.